This invention relates to ion microscopy and more particularly to a scanning transmission ion microscope.
The structure of thin samples can currently be analyzed by scanning transmission electron microscopes (STEM) or by transmission electron microscopes (TEM). Both of these instruments detect changes in the primary electron beam when it interacts with the electronic structure of a sample. The focused probe used in STEM will, upon exit from the sample, provide information about the atomic spacing in the material and the atomic species through interactions that are sensitive to the atomic number Z at the beam position. TEM illuminates the sample all at once with a uniform electron beam so that the structure of the sample being examined imparts spatial information onto the beam. By looking at either the bright field (electrons which are transmitted) or dark field (electrons that are scattered), different types of sample information can be extracted. A TEM is a large, complex, expensive tool utilizing very high energy electrons. The use of very high energy electrons is an operational burden. STEM is somewhat simpler but cannot yield the same resolution as TEM. Its main advantage is greater contrast dependence on Z, allowing species characterization.
Atomic level surface structure from thick samples is obtainable by scanning tunneling microscopy (STM) and, to a lesser extent, by atomic force microscopy (AFM). These are slow methods that require mechanically scanning a very fine needle-shaped tip over the sample. These methods cannot provide information on what is below the top atomic layer of the sample, however.
A detailed understanding of the operation of the above-mentioned, presently available microscopes is held by many persons skilled in the art of high resolution microscopes. Detailed information on the theory of operation and the applications of these microscopes is readily available in the public domain. Commonly available publications include, but are not limited to, classroom text books, scientific publications, microscope vendor publications as well as various documents commonly available in libraries such as the United States Library of Congress. There are also many patents that cover these commonly available microscopes. An example of a commonly available publication provided by a microscope vendor is JEOL News, Volume 37E, Number 1, 2002. Textbooks that teach the above described microscopes include the following:
1. Scanning Electron Microscopy and X-Ray Microanalysis by Joseph Goldstein (Editor)
2. Scanning and Transmission Electron Microscopy: An Introduction by Stanley L. Flegler, et al.
3. High Resolution Focused Ion Beams: FIB and Its Applications by Jon Orloff
4. Materials Analysis Using a Nuclear Microprobe by Mark B. H. Breese
5. Scanning Probe Microscopy and Spectroscopy: Theory, Techniques, and Applications by Dawn Bonnell (Editor)